The functional vessels of human and animal bodies, such as blood vessels and ducts, occasionally weaken or even rupture. For example, in the aortic artery the vascular wall can weaken, resulting in dangerous conditions such as aneurysms and dissections. Upon further exposure to hemodynamic forces, such an aneurysm can rupture.
One intervention for weakened, aneurismal, or ruptured vessels is the introduction of an endoluminal device or prosthesis, such as a stent graft, into a patient's vessel. These devices are designed to provide some or all of the functionality of the original, healthy vessel and/or preserve any remaining vascular integrity by reinforcing the portion of the vessel wall that contains the site of vessel weakness or failure. Stent grafts for endoluminal deployment are generally formed from a tube of a biocompatible material and one or more stents to maintain a lumen therethrough. Stent grafts can effectively exclude the aneurysm by sealing both proximally and distally to the aneurysm, such that the patient's blood flow is shunted through the stent graft. A device of this type can, for example, treat various arterial aneurysms, including those in the thoracic aorta, abdominal aorta, iliac, or hypogastric artery.
Two closely related aspects of stent graft function are sealing and fixation. A stent graft typically engages the wall of the lumen on both ends of the aneurysm or other defect, at proximal and distal regions referred to as landing or sealing zones. Typically these sealing zones are located near the termini of the stent grafts. The seal between the stent graft and the vascular wall is typically formed at these locations as a result of the circumferential apposition of the stent graft to the vascular wall, where this apposition is typically maintained by the radial force of the stents that are attached to the stent graft.
It is also desirable to fix, or anchor, the stent graft in place. For some abdominal aortic aneurysm stent grafts, proximal fixation in the neck region of the aorta is critical for long term durability of endoluminal repair. Fixation or anchoring of the stent graft can be achieved using a variety of anchoring mechanisms. One anchoring mechanism relies on the frictional forces that exist between the stent graft and aortic wall due to the radial force supplied by the stent. Fixation may also be achieved by using small hooks or barbs that extend from the stent graft and penetrate the arterial wall. Another method of anchoring the stent graft may involve tissue encapsulation, wherein exposed stent struts and other parts of the stent graft may eventually become completely encapsulated by tissue growth, thereby assisting fixation.
The stent and the graft material of endoluminal prostheses are often attached using hand-sewn sutures. Unfortunately, this method of attachment is labor-intensive, time-consuming, and expensive.
Another method of attaching the stent and the graft material of an endoluminal prosthesis is to cover the stent with an adhesive or a polymer coating that will allow the stent to be bonded to the graft material. Unfortunately, this type of attachment has several drawbacks. For example, these techniques often require multiple steps, since the stent must be treated with the adhesive or polymer coating before the process of attaching the graft can begin. Furthermore, the process of coating the stent with the adhesive or polymer coating usually requires multiple steps. Typically, the adhesive or coating is applied in a first step, using a variety of methods, and then must be cured in a subsequent step. In addition, once the adhesive or polymer coating has been applied to the stent and the graft material has been placed over or within the coated stent, actual bonding between the graft material and the adhesive, or the polymer coating, usually requires heating the coated stent and the graft material in an oven or other heating device. Unfortunately, this heating process limits the types of graft materials that can be used and may also affect the integrity of the graft material itself. In addition, this heating process may also thermoplastically fuse large portions of the graft material.